Integrated circuits have developed into enormously complex structures. Not only are there millions of devices in a state of the art integrated circuit, but the number of such devices tends to double every eighteen months or so. In addition to having a greater number of devices, integrated circuits are being fabricated with devices that are continually reduced in size, and disposed at ever decreasing distances one from another. Thus, integrated circuits are becoming smaller and more complex, all at the same time.
Because there are more and smaller devices within each integrated circuit, a physical defect on the substrate, such as may be caused by contamination or a processing flaw, tends to be very detrimental to the proper operation of the integrated circuit. One reason for this is that any defect on the substrate tends to impact the proper formation of one or more of the devices within the integrated circuit, since there are so many devices, and the devices are placed so close to one another. By way of comparison, in the past, when devices were generally larger and placed farther apart, there was more room on the substrate where a defect could occur, and which did not touch any of the devices of the integrated circuit, or perhaps was not the type of defect which would damage the few devices that it did touch. This situation no longer exists.
Thus, there is a great deal of attention paid to ensuring that the processes and materials that are used in integrated circuit fabrication do not contain or create defects on the substrate. For example, integrated circuits are typically formed on substrates that include a semiconducting portion, such as Group IV materials like silicon and germanium, or Group III-V compounds such as gallium arsenide, or composites of such materials. Much attention is given to ensure that these substrates are defect free at the on-set of processing, so that there are no known defects that would decrease the expected yield of the integrated circuits at the end of the fabrication process.
Similar precautions are taken with the other materials that are used during the fabrication process. For example, all of the gasses, liquids, metals, dielectrics, and organics that are used during the fabrication process are refined to an extremely pure state, so that they do not introduce materials that might behave in a unknown or undesirable manner during processing, or otherwise introduce defects, such as by contaminating the substrate.
Further, the processes that are used to fabricate the integrated circuits are inspected and controlled to a high degree, typically using techniques such as statistical process control, to ensure that the processes themselves do not create defects within the integrated circuits. For example, certain processes are closely watched to ensure that they do not create flakes or chips that might deposit onto the surface of the substrate, and thereby create defects in the integrated circuits. Process reaction chambers are periodically cleaned to prevent such flaking and other forms of contamination, so that the processing itself does not create defects.
Defect information, such as is determined by inspections during the fabrication process, is also correlated with electrical or other functional failures of integrated circuits, both at the testing down at the end of the substrate level fabrication process, generally known as wafer sort, and also after the individual integrated circuits are packaged, generally known as final test. Such correlations can be extended to a determination of whether the failure of the integrated circuit was due to a processing problem or a materials problem.
However, even though there is good correlation between processing problems and defects, and between materials problems and defects, and between defects and electrical failures, more information in regard to the correlation and correction of defect issues is needed. There is a need, therefore, for a system whereby defects are correlated with integrated circuit designs, such as the structures that are formed during integrated circuit fabrication.